Proper Condom

Hey guys, I'm pretty much 7.25" by 5.75" and whenever I try to use regular condoms I get a red ring around my shaft after I'm done with it. I've tried Magnums and regardless of how hard I pull they don't slide off. I'm curious if the red ring is a sign that I shouldn't be using them or not. I just have a problem thinking I need Magnums because I'm not huge.